W3Schools

HTML

HTML Tutorial

HTML Tag Referene

CSS

CSS Tutorial

CSS Reference

SQL

SQL Tutorial

SQL Reference

PHP

PHP Tutorial

PHP Reference

HTML/CSS

Learn HTML
Learn HTML5
Learn CSS
Learn CSS3

JavaScript

Learn JavaScript
Learn jQuery
Learn jQueryMobile
Learn AJAX
Learn JSON
Learn Google Maps

Server Side

Learn SQL
Learn PHP
Learn ASP
Learn ADO
Learn ASP.NET
Learn VBScript
Learn AppML

XML Tutorials

Learn XML
Learn DTD
Learn Schema
Learn XML DOM
Learn XPath
Learn XSLT
Learn XQuery
Learn XSL-FO
Learn SVG
Learn RSS
Learn WSDL

WEB Building

Web Primer
Web Building
Web Statistics
Web Validation
Web Certificates